• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1298-1301
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• 2003

The purpose of this research is to evaluate the effect of pre-load and fatigue life of the distracted one-level pedicle screw system. A spring, which acted as a substitute of the ligament, was installed in the one-level pedicle screw system before testing. The static and fatigue properties are now being tested, which includes 6mm rod to 6mm screw, 6mm rod to 6.5mm screw and 6.35mm rod to 6.5mm screw, under pre-load. Until now as test data were analyzed, 6mm rod to 6.5mm screw was found to have the best performances of stillness and fatigue lift, while 6mm rod to 6mm screw showed the shortest fatigue life. If the stiffness of screw was bigger than that of rod. the fatigue life was prolonged. The fatigue life of the distracted pedicle screw was proved to be shorter than that of the one-level pedicle screw system. So the fatigue life was shortened because of the effect of the spring on the flexibility and stiffness of the rod. In order to obtain the stability of the pedicle screw, more tests are under doing on this topic.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.38-50
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• 2018

Spatio-temporal load forecasting (STLF) is a foundation for building the prediction-based power map, which could be a useful tool for the visualization and tendency assessment of urban energy application. Constructing one point-forecasting model for each electricity cell in the geographic space is possible; however, it is unadvisable and insufficient, considering the aggregation features of electricity cells and uncertainties in input variables. This paper presents a new STLF method, with a data-driven framework consisting of 3 subroutines: multi-level clustering of cells considering their aggregation features, load regression for each category of cells based on SLS-SVRNs (sparse least squares support vector regression networks), and interval forecasting of spatio-temporal load with sampled blind number. Take some area in Pudong, Shanghai as the region of study. Results of multi-level clustering show that electricity cells in the same category are clustered in geographic space to some extent, which reveals the spatial aggregation feature of cells. For cellular load regression, a comparison has been made with 3 other forecasting methods, indicating the higher accuracy of the proposed method in point-forecasting of spatio-temporal load. Furthermore, results of interval load forecasting demonstrate that the proposed prediction-interval construction method can effectively convey the uncertainties in input variables.

• Korean Journal of Agricultural and Forest Meteorology
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• v.1 no.1
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• pp.36-40
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• 1999

A new method was developed to measure underground water level with high reliability. The principle of new method was to detect a change of a buoyant force according to change in water level of underground water measured by the use of a straingage load cell. Field test of the instrument was carried out in Cheju Island. The results were as follows; 1) The present study provided a possibility to develop a new underground water level meter. 2) This new instrument accomplished high reliability at field test in Cheju Island. 3) There is possibility of development of water level meter which measure various range of water level to detect a weight change of a buoyant forcd.

• KCI Concrete Journal
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• v.12 no.1
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• pp.113-120
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• 2000

This paper presents the behavior and strengthening effect of reinforced concrete rectangular beams strengthened using CFRP sheets with different strengthening level. In general, normally strengthened beams are failed by interfacial shear failure (delamination) within concrete, instead of by tensile failure of the CFRP sheets. The delamination occurred suddenly and the concrete cover cracked vertically by flexure was spalled off due to the release energy. The strengthened beams were stiffer than the control beam before and after reinforcement yielding. The ultimate load considerably increased with an increase of strengthening level, while the ultimate deflection significantly decreased. The tensile force of CFRP sheets and average shear stress of concrete at delamination failure were curvilinearly proportional to the strengthening level. Therefore, the increment of ultimate load obtained by strengthening was curvilinearly proportional to the strengthening level. The averaged horizontal shear stress of concrete at the interface ranges between (equation omitted) and (equation omitted) (in kg/$\textrm{cm}^2$) depending on strengthening level.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.10a
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• pp.356-363
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• 2000

The objectives of this study are to investigate seismic performance of spirally reinforced bridge columns and to provide test result for developing improved seismic design criteria. Quasi-static test was conducted for 12 columns of which variables were transverse reinforcement ratio and spacing, longitudinal reinforcement ratio, and axial load level. Sufficient seismic performance was observed from the test for the columns with greater confinement steel amount than the requirement of the Korean Bridge Design Specification. The columns with 0.84% of the confinement steel requirement provided adequate performance under less than 0.2 of axial load level, but showed lower ductility under 0.3 of axial load level. The current provision for the region of confinement steel distribution may be non-conservative under high axial load level, therefore a modified provision is proposed.

• Journal of Industrial Technology
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• v.9
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• pp.43-49
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• 1989

In this study, 3-point bending test for the mode I state and 4-point shear test for the mode II state were adopted to verify the crack initiation load level through comparing the test results of the acoustic emission and the ASTM testing criteria, using Jecheon granite, as the rock sample. The major result obtained in this study is that the crack initiation load levels obtained by using ASTM testing criteria and by measuring acoustic emissions showed analogous, roughly. However in case of demanding high safety, the crack initiation load level needs to be underestimated to the level that the crack begins to deform nonlinearly.

• Journal of the korean Society of Automotive Engineers
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• v.15 no.3
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• pp.111-119
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• 1993

In this study, the transient impact structural stress analysis of tracked vehicle structures under recoil impact load is investigated. ANSYS, ABAQUS Code are used for modelling and analytical procedures. The highest maximum Tresca stress occurs on race ring portion and its stress level is (.sigma.$_{T}$)$_{max}$ =20-40kgf/m $m^{2}$. The second highest stress occurs on upper plate of chassis and down plate of turret. The maximum stress level increases with loading direction and elevation angle. The results from liner static load analysis are very much different with impact analysis. Therefore, the practical solutions of structures under impact load can be obtained by only nonlinear transient impact analysis. The impact stress analysis of the steel vehicle structures is conducted. The maximum stress level is less than (.sigma.$_T/)$_{max}$m $m^{2}$. So, the design concept of steel structures can be adapted for new alternatives.s.s.s..s.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.9
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• pp.494-499
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• 2004

This paper presents to compute the power economic dispatch, an optimal power flow (OPF) computation algorithm, considering the load power factor limits constraint in developed. Efficient reactive power planning enhances economic operation as well as system security. Accordingly, an adequate level of power factor limits for the load busesshould be evaluated for economic operation. In this paper, the ranges of acceptable load power factors are portrayed as bandwidths of load power factor expressed as a function of load level. The load power factor limits are included and described into the OPF's objective function. The method Proposed is applied to IEEE 26 bus system.

• Educational Technology International
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• v.13 no.1
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• pp.79-100
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• 2012

The focus of this research is on identifying the problems that learners experience during online problem-based learning (e-PBL) from a cognitive perspective. The study is concentrated on learners' cognitive load level at each stage of e-PBL. The research questions are specifically as follows: What is the level of cognitive load at each stage of e-PBL and what is the relationship between cognitive load and group performance? What cognitive difficulties are experienced by learners in e-PBL and what causes cognitive difficulties? In this study, we found that cognitive load was the highest in stage 1 and there was negative relationship between cognitive load at stage 1 and group performance. In addition, learners experienced difficulties during e-PBL such as the complexity of task, the difficulty in collaboration, and the lack of appropriate references. For further study, we will investigate some strategies regarding adjusting learners' cognitive load in the early stages of e-PBL.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.10
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• pp.1187-1191
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• 2011

In this paper, the development of an adjustable load limiter is presented, which is a component of the seat belt. The adjustable load limiter is loaded at different levels for varied weights and heights of occupant. The recent regulation FMVSS 208 demands strict safety standards for different percentiles of dummy size. In this work, high- and low-level load conditions are proposed according to dummy scale and thoracic injury criteria. The suggested load conditions were verified by performing a sled test using the benchmark model. A dual-level load limiter has been developed on the basis of these tests. Experiments were conducted on the product performance, and finite element analysis was carried out; the results confirmed the points for improvement.